From the viewpoint of energy saving, an illumination apparatus using a light emitting diode (LED) as a light source is becoming widely used. However, since the LED has a short afterglow characteristic, a space around the illumination apparatus becomes dark immediately when the power supply to the illumination apparatus from an external power source stops. Thus, an illumination apparatus which can emit an afterglow for a few seconds or minutes after stopping the power supply to the illumination apparatus from an external power source has been proposed (see, e.g., Japanese Unexamined Patent Application Publication No. 2013-4960).
FIG. 12 is a diagram showing a circuit configuration of an illumination apparatus 900 disclosed in Japanese Unexamined Patent Application Publication No. 2013-4960. The illumination apparatus 900 includes two light emitting modules 911 and 912 using LEDs as a light source, a constant current output circuit 921, two capacitive elements 922 and 924, a diode 923, a zener diode 925 and a resistor 926.
In the illumination apparatus 900, during normal lighting in which power is supplied to the constant current output circuit 921 from the external power source, as shown by a solid arrow in FIG. 12, first, the capacitive element 922 for ripple suppression is charged from the constant current output circuit 921. When charging to the capacitive element 922 is completed, power is supplied to the light emitting module 911 and the light emitting module 911 is turned on. When the power is supplied to the light emitting module 911, as shown by another solid arrow in FIG. 12, charging to the capacitive element 924 through the diode 923 is also performed.
On the other hand, when the power supply to the constant current output circuit 921 from the external power source is stopped, the power supply to the light emitting module 911 and the capacitive elements 922 and 924 from the constant current output circuit 921 is not performed. However, as shown by a dashed arrow in FIG. 12, the charges accumulated in the capacitive element 924 flow to the light emitting module 912 and the light emitting module 912 is turned on. Thus, even after the power supply to the constant current output circuit 921 from the external power source is stopped, while the charges remain in the capacitive element 924, the light emitting module 912 can be turned on by using the charges. Therefore, light emitted from the light emitting module 912 can be used as an afterglow.
In the illumination apparatus according to Japanese Unexamined Patent Application Publication No. 2013-4960, in addition to a capacitive element for suppressing the ripple current used in normal lighting, it is necessary to further provide a capacitive element used as a power source for providing the afterglow. Since the capacitive element is a relatively large component among the circuit components, it is preferable to reduce the size of the illumination apparatus by reducing the number of capacitive elements as much as possible. In particular, it is expected that the illumination apparatus using LEDs as a light source will replace a conventional illumination light source such as an incandescent bulb, a fluorescent lamp, and a high-pressure discharge lamp. Therefore, miniaturization of the illumination apparatus is important in terms of increasing conformity with the existing luminaire.